This invention relates to a protective beacon for warning of potential hazards. Specific aspects of the invention relate to the hazards presented in use of aircraft refuelling protection systems, which systems will be used hereinafter in describing the invention and its benefits.
Aircraft refuelling systems in use at most substantial airports incorporate an underground hydrant system including a network of fuel storage tanks buried in the airport apron. The storage tanks communicate through pipework and valves in a ring main system leading to a plurality of refuelling pits. Each refuelling pit contains a valved pit head and a removable cover that, when in place, lies flush with the surrounding surface of the apron. When removed, the cover permits access to the pit head so that a nearby aircraft can be refuelled by fuel flowing through the pit head.
The underground refuelling network is pressurised and maintains fuel pressure through a series of automatic inline pumps. These pumps operate automatically in the event of a detected drop in fuel pressure, for instance when an aircraft begins to take fuel from the refuelling network, so that there is sufficient pressure to refuel more than one aircraft simultaneously.
In aircraft refuelling systems of this type, a refuelling support vehicle, or hydrant dispenser, provides the link between an aircraft and a refuelling pit. The purpose of the hydrant dispenser is to monitor the quantity and quality of fuel dispensed to the aircraft. Accordingly, the hydrant dispenser is positioned adjacent the aircraft""s refuelling point to meter and filter fuel flowing from the pit head to the aircraft, for which purpose the hydrant dispenser is connected to the pit head by a fuelling pipe or hose and to the aircraft by another pipe or hose. The hydrant dispenser may also carry these pipes on spools when not in use, together with any attachments, couplings or connectors necessary to attach the pipes to the aircraft and the pit head.
The operator of the hydrant dispenser is responsible for the operation, integrity and safety of the vehicle and of the pipes and couplings constituting the fuel line or conduit between the aircraft and the pit head.
Accidents can happen on airport aprons and if they do, they can have serious consequences in view of the presence of fuel-laden pipes and adjacent fuel-laden aircraft. The vehicles and machinery used on airport aprons are often large with invisible extremities, and so are difficult for their operators to position accurately. This increases the risk of collision with refuelling equipment during refuelling. Furthermore the environment in which aircraft refuelling takes place is often noisy and physically demanding, making it difficult to hear shouted warnings that a collision is imminent. All of these factors contribute to the likelihood of a fuel pipe being snagged and fractured, or of the coupling between the pipe and the pit head being knocked and the seal broken.
The most likely section in a refuelling network for a collision to occur and cause a fuel leak is in the link between the hydrant dispenser and the refuelling pit. The coupling at the pit head and the refuelling pipe that leads from the coupling to the hydrant dispenser do not rise much above ground level and are relatively small compared to the scale of the surrounding machinery, making them easy to miss.
It might be thought that even if a collision did occur and cause a fuel leak, it would simply be a matter of closing a valve to prevent, contain or extinguish a resulting fire by starving it of fuel. Unfortunately, this is not so. It is not practical for the pressure control means of the system to differentiate between a normal drop in fuel pressure that occurs during refuelling and a pressure drop that might have occurred due to a leakage in the refuelling network. In fact, it has happened that after an accident has caused a leak in the refuelling network, the pressure control means of the system has switched on additional pressurisation pumps in an attempt to restore fuel pressure in the ring main system, thereby worsening the already dangerous situation by pumping ever more fuel to the site of the leak. A simple fracture in an aboveground fuel conduit can therefore cause an uncontrolled gusher of fuel, which will almost certainly catch fire. The potentially catastrophic consequences of this happening close to fuel-laden aircraft need no elaboration.
Current practice to prevent such accidents involves placing one or more warning flags and warning cones around the vicinity of a refuelling operation when the hydrant dispenser has a live fuel connection. Further, current practice involves providing a refuelling operator with a lanyard that the operator can pull as a last resort to close the valve on the pit head to stop the flow of fuel in an emergency. The operator must therefore keep a close watch for moving vehicles around the aircraft and the refuelling area so that if the operator fears that a collision may occur, he pulls the lanyard in an attempt to shut down the refuelling pit before the collision actually happens.
The current practice as described above is unsatisfactory as it relies upon alertness of the refuelling operator and human intervention to pull the lanyard in time. So, it fails if the operator is incapacitated, slow or unobservant, and also because the lanyard itself might not work in an emergency situation. For example, instances have been documented of a vehicle colliding with a refuelling pipe or coupling and the lanyard being trapped beneath a wheel of the vehicle in a manner that prevents the valve being closed by pulling on the end of the lanyard. Also, whilst pit heads have a fail-safe design, it is possible that a major collision could prevent the lanyard closing the valve at all.
The invention embodies a principle, namely that a portable beacon can be positioned to deter damaging access to a deactivatable hazard, the beacon including means for deactivating the hazard in the event of impending damaging access to the hazard and proximity sensor means responsive to the proximity of a threat, wherein the proximity sensor means is responsive to the distance of the threat from the beacon. The principle can also be expressed as a method of protection against a deactivatable hazard, the method comprising positioning a portable beacon to deter damaging access by a threat to the hazard and the portable beacon deactivating the hazard in response to proximity of the threat to the beacon.
Thus, the invention has application beyond the field of fuel supply and storage systems but it has particular benefits in that field. Against this background, therefore, the invention can be expressed as a beacon adapted to deter damaging access to a fuel conduit, the beacon including means co-operable with the conduit to shut off fuel flow through the conduit in the event of actual or impending damaging access to the conduit. The invention can also be expressed as a beacon adapted to deter damaging access to a fuel conduit, the beacon including a valve for exhausting pressurised air to atmosphere from an air line associated with the conduit to shut off fuel flow through the conduit controlled by the air line.
Again, the fuel supply and storage aspect of the invention can be expressed as a method of preventing uncontrolled leakage of fuel through collision damage to an exposed conduit in a fuel supply or storage system, the method comprising positioning a portable beacon to deter collision by a threat with the conduit and in the event of actual or impending collision with the beacon, the beacon co-operating with the conduit to shut off fuel flow through the conduit in response to proximity of the threat to the beacon.
The invention extends to a safety system including a deactivatable hazard and a portable beacon as defined herein, especially when the beacon is positioned to deter damaging access to the hazard and is linked to the hazard for the purpose of deactivation.
The invention also embraces a fuel supply or storage system, the system comprising a portable beacon as defined herein adapted to deter collision with an exposed fuel conduit, the beacon including means co-operable with the conduit to shut off fuel flow through the conduit in the event of actual or impending collision with the beacon to prevent uncontrolled leakage of fuel through collision damage to the conduit. The advantages of the invention are particularly apparent where the fuel supply or storage system is adapted to refuel aircraft.